The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Automatic shifting motor vehicle transmissions include a hydraulic system, which provides power and controls operation of the various clutches, brakes and other elements within the transmission. The hydraulic pressure is limited or controlled in value to provide the most efficient operation that can be obtained.
In more recent transmissions, the hydraulic controls have been advanced to electro-hydraulic controls wherein electrical or electronic signals are available to assist transmission control. The electro-hydraulic controls generally comprise a solenoid valve, which receives various signals from a transmission control module (TCM) to supply a pressure signal to the various operating valves of the transmission. During an engine start event, there may be a marked increase or decrease in the pressure level of a passage that supplies fluid to the clutches. This increase or decrease results in an increase or reduction of torque capacity in the clutch. This change in torque capacity affects the vehicle launch performance. For example, a reduction in torque capacity increases the amount of time for the vehicle to reach a desired level of acceleration. Therefore, while current electro-hydraulic controls achieve their intended purpose, there is a need in the art for an electro-hydraulic control system that provides fluid to the clutches at a more constant pressure level.